Manufacturing of microelectronic devices entails creating complex three-dimensional structures via laborious layer-by-layer process, where most steps rely on wet chemistry or gas-phase chemistry, require a multitude of expensive machines, and generate large quantities of toxic waste. It would be advantageous to replace these processes with more efficient methods such as, printing techniques used in graphic arts or similar alternatives, where the desired structure is deposit on demand and does not require waste-generating, post-processing steps (e.g. deposition and removal of photoresists, etching, cleaning, etc.). However, silicon—the main material used in semiconductors—cannot be formulated into liquids as it does not melt or dissolve at convenient temperatures (below 500 DEG C., preferably below 100 DEG C.). To overcome this complication, various gaseous and liquid hydrosilanes and hydrogermanes (silicon hydrides and germanium hydrides) are utilized as precursors, which can decompose to loose hydrogen and yield silicon and germanium.
Hydrosilanes composed entirely of hydrogen and silicon atoms, are more precisely called perhydrosilanes, but in practice prefix “per” is often omitted. Accordingly, hydrogermanes composed entirely of hydrogen and germanium atoms, are more precisely called perhydrogermanes, but in practice prefix “per” is often omitted. Simple perhydrosilanes, such as monosilane (SiH4) and disilane (Si2H6) are widely used in semiconductor manufacturing. For example, a device such as a thin film transistor is conventionally manufactured by using monosilane gas to form a silicon film on a surface via a vacuum process such as thermal CVD (chemical vapor deposition), plasma enhanced CVD, or photo-assisted CVD. Unfortunately, CVD exhibit the following limitations. (a) The production yield is low due to system contamination and the formation of foreign materials, which are caused by silicon particles generated during the gas phase reaction. (b) A uniform film thickness is barely obtainable on a substrate having an uneven surface due to gaseous raw materials. (c) The productivity is low due to a low deposition rate of the film. (d) The necessary vacuum equipment is complicated and expensive, particularly for treatment of large area substrates.
Furthermore, CVD yields film covering large areas of the substrate, and the unnecessary portions of the film are subsequently removed through photolithography and etching. The utilization efficiency of raw materials is low, and a large quantity of waste is produced. In regard to materials, use of silicon hydride, which is highly reactive gas, causes difficulty in handling and requires hermetic vacuum equipment. Since these apparatuses are complicated, the apparatuses themselves are expensive. Moreover, the vacuum system and the plasma system consume a large amount of energy, resulting in high production costs.